Half-blood
Half-blood was the term commonly given to wizards and witches who had known Muggle or Muggle-born ancestry. By the 1990s, half-bloods were the most common type of magical person, as the pure-blood wizarding population would have become extinct had they not inter-married with Muggles and Muggle-borns. "The expressions 'Pure-blood', 'Half-blood' and 'Muggle-born' have been coined by people to whom these distinctions matter, and express their originators' prejudices. As far as somebody like Lucius Malfoy is concerned, for instance, a Muggle-born is as 'bad' as a Muggle. Therefore Harry Potter would be considered only 'half' a wizard, because of his mother's grandparents. If you think this is far-fetched, look at some of the real charts the Nazis used to show what constituted 'Aryan' or 'Jewish' blood. I saw one in the Holocaust Museum in Washington when I had already devised the 'Pure-blood', 'Half-blood' and 'Muggle-born' definitions, and was chilled to see that the Nazis used precisely the same warped logic as the Death Eaters. A single Jewish grandparent 'polluted' the blood, according to their propaganda." However, if you went back far enough all the Pure-bloods, would technically all be Half-bloods Overview It should be noted that any wizard who is neither Pure-blood nor Muggle-born is considered a Half-blood, even if they have two wizard parents; they need not have exactly half-Muggle/half-wizard heritage. Non-magical children born with at least one magical parent are considered Squibs by the wizarding community rather than Half-bloods or Muggles. Examples include Martha Steward II, Dolores Umbridge's brother, and Gilderoy Lockhart's two sisters. Because of their Muggle parentage, many end up assimilating into the Muggle population as they would have more trouble thriving within the magical community although some are able to carve out niches for themselves such as Argus Filch. Treatment Those who believe in the importance of blood purity consider Half-bloods to be inferior because of their Muggle heritage, though superior to Muggle-borns. As such, some families such as the Malfoys allowed them to marry into their Pure-blood family and could do so without affecting their family's Pure-blood status. "From the imposition of the Statute of Secrecy onwards, no Malfoy has married a Muggle or Muggle-born. The family has, however, eschewed the somewhat dangerous practise of inter-marrying within such a small pool of Pure-bloods that they become enfeebled or unstable, unlike a small minority of fanatic families such as the Gaunts and Lestranges, and many a Half-blood appears on the Malfoy family tree." Other more fanatical families such as the Gaunts, Lestranges, and Blacks, require all marriages to be those of Pure-blood. Members of these families are more likely to use "Half-blood" in a derogatory manner, similar to the epithet "Mudblood"; Bellatrix Lestrange did so on multiple occasions, and the portrait of Walburga Black often equated half-bloods with Half-breeds. Some half-bloods expressed prejudice towards those with Muggle heritage, despite having some themselves, and clung to what wizarding heritage they had. Notably Lord Voldemort persecuted Muggles and Muggle-borns, despite the fact that his mother (Merope Gaunt) was a pure-blood witch and his father (Tom Riddle Snr) was a Muggle. He denied his Muggle heritage, instead emphasising his wizard ancestors; his legend-entitled nickname was "''Heir of Slytherin''" because his most notable wizard ancestor (Salazar Slytherin) was a famous Pure-blood champion, which made himself more believable. Severus Snape may be another example; his self-entitled nickname was "''Half-Blood Prince''" because his mother (Eileen Prince) was a pure-blood witch and his father (Tobias Snape) was a Muggle. However, Remus Lupin reported that he never used the nickname openly. This, as well as Snape's membership in the Death Eaters, suggests he may have been ashamed of his Muggle heritage, at least in his early life. In fact, these people, along with some other Death Eaters, pretend to be Pure-bloods, hiding their Muggle heritage from anyone else. - "The Death Eaters can’t all be Pure-blood, there aren’t enough Pure-blood wizards left,” said Hermione stubbornly. “I expect most of them are Half-bloods pretending to be pure. It’s only Muggle-borns they hate, they’d be quite happy to let you and Ron join up.” Ironically (or perhaps because of), regarding the prophecy concerning his defeat, Voldemort chose to go after the Half-blood Harry Potter instead of the pure-blood Neville Longbottom. When the Ministry of Magic fell under Voldemort's control in 1997, Muggle-borns were openly persecuted and pure-bloods were favoured above all else. Half-bloods were still accepted at Hogwarts School of Witchcraft and Wizardry and in the British Ministry of Magic, but were not treated as well as the Pure-blood members. -Neville: "They don’t want to spill too much pure blood, so they’ll torture us a bit if we’re mouthy but they won’t actually kill us."